Such an optical light guide element is known form International application WO 2012/071674. This International application relates to an optical light guide element having a first end section with a light entrance area designed for facing a light source and having a second end section with a light exit area designed for facing a light target area, wherein the light entrance area is defined by a surface area on the optical light guide element which faces the light source and wherein the first end section comprises an inclined surface area which forms an acute angle with the surface area of the light entrance area.
JP2006337641 relates to a method for producing prisms having high angular accuracy wherein a laminated glass is obtained by bonding small and large substrates orderly. Subsequently, the glass laminate is cut into several pieces and double side polishing is carried out, wherein the cut glass pieces are divided into short strips by cutting at intervals more than the length of prism in orthogonal to the polishing surface. The short strips are polished along the cut surface with respect to the reference plane and strips are again cut at equal spacing in orthogonal to the polishing surface of double side polishing or short strip polishing.
JP 2010-122576 relates to a method for manufacturing an optical element having at least one optical thin film having a predetermined optical function inside the element, wherein the method includes a laminate joined body-forming step of laminating a plurality of sheets of parallel planar optical components so that the optical thin film and an adhesive are interposed between the components to form a laminate joined body.
WO2013049948 relates to a method for manufacturing an optical element, comprising the steps of providing a wafer comprising a multitude of semi-finished objects, separating said wafer into parts referred to as sub-wafers comprising a plurality of said semi-finished objects, processing at least a portion of said plurality of semi-finished objects by subjecting said at least one sub-wafer to at least one processing step. A light guide element is manufactured starting from a blank transparent glass or polymer wafer which is on both sides provided with a coating such as a sputtered aluminium reflective coating which then is selectively etched using lithography for forming transparent light entrance areas. This light guide element is a part of the final optical path and should therefore be transparent. The wafer according to WO2013049948 comprises a multitude of semi-finished products obtained involving carrying out, e.g., one or more of lithographic processes, replication processes, coating processes, mechanical processes, etching processes, polishing processes and/or others. The wafer is divided into sub-wafers, e.g., by punching, sawing, cutting, or laser cutting, a sub-wafer comprising one or more, usually a plurality of said semi finished products. Then the sub-wafers are processed, wherein the processing may comprise one or more of lithographic processes, replication processes, coating processes, mechanical processes, etching processes, polishing processes and/or others. Then, the processed one or more sub-wafers are separated into a multitude of objects. The so-obtained objects may be used as obtained or may be subjected to further processing, e.g., to a packaging process or to a mounting process in which the object is mounted to another element or device. Polishing steps of optical surfaces may result in damaged optical surfaces.
Such is for example known from US 2012/0176685. US application 2012/0176685 relates to a refractive, variable magnification optical system including, sequentially from a side nearest an object, a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power. In addition, the first lens group includes sequentially from the side nearest the object, a negative meniscus lens having a convex surface facing toward the object, a prism that refracts an optical path, a plano-convex lens, and a biconvex lens, a light transmitting surface of the prism and the planoconvex lens being cemented.
Although US 2012/0176685 teaches a demand for smaller imaging apparatuses and smaller imaging lenses mounted to the imaging apparatuses, the solution provided by this document, i.e. a refractive optical system that disposes in the optical path, a prism that refracts the optical path, thereby enabling a reduction in a dimension of depth (thickness) of the optical system, does not provide a substantial reduction of the thickness of the imaging device while maintaining high optical performances, such as wider fields of view and higher resolution.
JP2008083197 relates to a method for producing a planar optical waveguide having a first cladding layer of one or both the lens structure and the second cladding layer, wherein the optical waveguide is suitably used as such a light coupling member in an optical interconnection which has a light source such as a VCSEL.
JP2005010645 relates to process for the preparation of the optical waveguide film, in particular to a method for producing optical waveguide film to be used for optical interconnection.
U.S. Pat. No. 7,421,163 relates to free space optical communications, in particular to free space optical detection with large field of view for use in optical communication systems.
FR 2 569 015 relates to a duplexer which optically couples a first, light-emitting optoelectronic component and an optical fibre acting as a receiver and the coupling of the said optical fibre, acting as an emitter, and a second, light-receiving optoelectronic component.
GB 2 289 138 relates to a multiple light path apparatus for a wireless optical communication system wherein at least a reflective layer (RL) within a lens forms an entry or end portion for a beam waveguide said layer (RL) forming an angle with the optical axis of the lens.
EP 0 209 108 relates to an optical element comprising at least two parts joined together, wherein the joining surface has an inclination to the optical axis and a beam splitter film transmits that caused by their reflection/transmission characteristic, a pitch and or collection of optical beams, wherein at least one of the boundary surfaces of the optical element comprises a converging or diverging optical effect.
U.S. Pat. No. 5,138,687 relates to a rib optical waveguide and an optical waveguide layer device including an optical waveguide layer or film on which a grating, a waveguide lens, etc. are formed and to a method of manufacturing the rib optical waveguide, the optical waveguide devices, and the optical waveguide layer devices by use with liquid materials which are solidified through an energy irradiation of ultraviolet ray and the like.
Many mobile devices, such as mobile phones and tablet computing devices include cameras that may be operated by a user to capture still and/or video images. Because the mobile devices are typically designed to be relatively small, it can be important to design the cameras or imaging systems to be as thin as possible in order to maintain a low-profile mobile device. In various conventional devices, the thickness of the mobile device is maintained as small as possible by turning either the image sensor or the lens group on its side and using reflective devices to bend the rays to the sensor. It is also possible to maintain the thickness of the mobile device as small as possible by shortening the focal length of the imaging system.
In addition, slanted optical surfaces on mirrors, prisms, beam splitters and in periscopic systems are used for light beam deflection, reflection and beam splitting at 90 degrees (45 deg slope) in e.g. interferometry and encoders. At a much smaller scale (features sizes far below 500 micron) similar structures can be found in displays and planar optics embedded on silicon substrates' for telecom applications.
Folded optics and similar periscopic optical systems are also increasingly used for imaging and light guide applications in mobile imaging, optical sensors and other consumer applications. Because the devices are becoming thinner, folded optics becomes in many case the only solutions for decreasing the size of the camera optics; the height in particular. For instance, diameters lenses or light guides are shrinking from 5 mm towards 1 mm. The present inventors found that assembly and precise alignment of slanted optics at these small dimensions becomes cumbersome, slow and very expensive.